The Head of the Turkish Presidency of Defense Industries, Ismail Demir, said Ankara and Moscow have no difficulties in terms of their obligations with regards to Russia's S-400 anti-aircraft systems.

Demir asserted that each party is determined to fulfill their obligations, and that there are no contractual issues between the two. 

"The process took a long time, as it required the implementation of the provisions of the agreement, application in the field, and additional technical tests. There are no questions regarding the contract and contacts on it," Demir told reporters on the sidelines of Turkey's Antalya Diplomacy Forum.

Furthermore, he asserted that Turkey has no interest in purchasing US Patriot missile systems, and that Russia's S-400 will provide Turkey with a great advantage in air defense.

"As for air defense systems, we can say the following: at present, we have four types of air defense systems in service, 3-4 years ago their number was zero," he noted.

Turkish Defense Minister Hulusi Akar confirmed in November that the Russian S-400 missile system will be used within NATO, akin to the S-300 system.

S-400 - F35: Erdogan demands lifting of Washington sanctions on Turkey 

In a phone call with Biden on Thursday, Erdogan demanded the lifting of the sanctions Washington had imposed on Turkey in 2019 after it announced its intent to purchase Russia's S-400 defense system.

Turkey has plans to acquire some 40 F-16 fighters, and the spare parts needed to maintain and modernize its existing fleet of F-16s after the US froze its purchase of F-35s following the 2019 Turkish acquisition from Russia.

Turkey had spent $1.4 billion ordering F-35 stealth fighters, but the order never made it through because of Washington's sanctions.

Military experts see the S-400 as a threat for F-35 jets, which prompted the US to exclude Turkey from its military program.